Diagonal Put Spread Calculator

By Yojana Mandon · Updated June 2026 · 3 min read · Risk disclaimer

A diagonal put spread sells a near-term out-of-the-money put and buys a longer-dated put at a different strike. It is the bearish mirror of the diagonal call: you collect near-term time decay while the longer-dated long put defines the risk and carries the directional view.

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Key characteristics

• Sell a near-term put, buy a longer-dated put at a lower or different strike.
• Profits from near-term time decay on the short put plus a downward drift.
• The long-dated put caps the risk and can be kept after the short put expires.
• A repeatable, income-plus-direction structure you can roll month to month.

When to use a diagonal put spread

Use it when you are mildly bearish or expect a slow grind lower and want to be paid to wait. Each cycle, the short near-term put decays in your favour, while the longer-dated long put holds value and gives you downside exposure if the move accelerates.

It is the bearish counterpart of the poor man’s covered put / diagonal call family. After the short put expires or is closed, you still hold the long put and can sell another near-term put against it, lowering your cost over time.

Risks and management

The main risk is a sharp drop straight through the short strike early, before time decay helps, or a rally that bleeds the long put’s value. Because the two legs have different expirations, the payoff at the near expiration is model-based, not a simple kinked line.

Roll the short put down and out to follow the stock and keep collecting premium, and watch the long put’s remaining time value — the structure works best when near-term decay outruns the slower decay of your long leg.

On the Greeks, the Diagonal Put Spread is vega-positive — rising implied volatility helps it, while an IV crush works against you, and theta-negative, so time decay erodes it and the move needs to come reasonably soon.

Managing the trade and common mistakes

Most experienced traders exit a diagonal put spread when it has captured roughly 50–70% of its maximum theoretical value, and they do this well before the short put expires. The optimal moment is when the underlying has declined toward — but not sharply through — the short strike. At that level the short put carries substantial time value while the long put has gained delta, and the spread commands its highest price. If the stock drops far below the short strike, the short put deep in the money loses its time-value advantage; the spread then behaves more like a vertical, and the extra premium you paid for the longer-dated long put becomes dead weight. When that happens, close or restructure rather than hoping for a bounce.

Rolling the short put is the core adjustment tool. When the short put nears expiration and the underlying is still near your target strike, buy back the short leg and sell a new put — typically at the same or a nearby strike in the next monthly cycle — collecting additional credit to extend the theta-harvesting engine. If the stock rallies sharply away from the short strike, the short put loses value quickly; that is good for the position today, but the long put also bleeds delta, so the spread can erode faster than intuition suggests. In a sharp rally, consider rolling the short put up to a strike closer to the new price level to re-center the trade. Cut the loss when the spread has fallen to about 25% of the original debit paid.

Early assignment on the short put is the liquidity nuance beginners most often overlook. Deep-in-the-money short puts on single stocks carry real assignment risk, especially when remaining time value is thin — the holder may exercise early to capture a dividend or simply to go long shares. If assigned, you are suddenly long the shares at the short strike while your long put remains open; manage that delta exposure immediately. On the structural side, avoid mismatching expirations: selling a short put that expires too close to the long put collapses the calendar premium differential and leaves almost no edge. Always use limit orders and price the spread as a single unit — wide bid-ask spreads on the back-month leg are the fastest way to give back an edge that looks attractive on paper.

Calculate it live

Use the free OptionProfit Diagonal Put Spread calculator to load a live option chain, build the trade, and instantly see the payoff chart, breakevens, probability of profit, Greeks and a Monte Carlo simulation of outcomes.

Frequently asked questions

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